Could you please define Rh factor in two to three sentences?

The Rh factor is also known as the Rhesus factor. It is named from the Karl Landsteiner and Alexander S. Weiner experiments in 1937. There are types of blood: A, B, O, and AB. Every type is also identified as positive or negative. This negative and positive label is used as a reference to the Rhesus factor of the blood. Rh positive have the Antigen present in their blood, while a Rh negative person does not have the Antigens. If a person has a blood type of A and has the Rhesus factor they are considered to be A-positive, or A+, blood. If people are missing the antigen, they are Rh-. I am B negative and I have a twin who is B positive. She has the antigens and I don’t.

“More than 85% of people are Rh-positive. People without the Rhesus factor, that is, people that don't have the antigen in their blood, are Rh-negative.”